The purple and blue one is made out of dollar tree foam. The paper was falling off the top side, so i took it off. The plane just didn't feel sturdy enough to survive a landing.
The second one , red, white, and blue one I built out of pink fff. It is modified a bit from the original plans. I added 2" to the front of the fuselage, and reinforced it with wood dowels. It flies great. Except for the prop saver bands breaking, forcing me into the pavement more than once.
The third one is built from Hobby Lobby foam board, which seems much more sturdy and the paper doesn't fall off. I haven't finished yet. It needs the firewall, reinforcement in the front of fuse and the servos/control linkages.

i used wood dowels to support the main . the horizontal stabilizers were very week on the dollar tree foam. covering it in tape might help this one. but the fff one and the hobby lobby ones feel so much sturdier .